<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>

    <div class="box">
        全选<input type="checkbox" class="checkAll"> <br>
        <span class="del">删除</span> <br>
        <span class="add">+</span> <br>
        <span class="add">+</span> <br>
        <span class="add">+</span> <br>
        <span class="reduce">-</span>  <br>
    </div>


    <script>

        var oBox = document.querySelector('.box') ;

        oBox.addEventListener('click' , function(e) {

            // console.log(e.target);  // 对应的标签


            if(e.target.className === 'checkAll') {
                console.log('点击了全选');

                return ;
            }

            if(e.target.className === 'add') {
                console.log('点击了加号');

                return ;
            }

        })
        
    </script>
    
</body>
</html>